A conventional ignition apparatus for supplying power to an ignition coil of an internal combustion engine is implemented by a semiconductor power module as disclosed in JP-2000-179440A (hereafter “patent reference 1”). FIG. 8 is a circuit diagram showing the semiconductor power module disclosed in patent reference 1 and FIG. 9 is a diagram showing a perspective view of a model of the module. The semiconductor power module is explained by referring to the figures as follows. Reference numeral 1 denotes a power semiconductor chip and reference numeral 2 denotes a ceramic board on which a control semiconductor chip (not shown) is mounted. The ceramic board 2 is a hybrid integrated circuit. The control semiconductor chip is a chip for implementing a current detection circuit 3, a driving circuit 4 and a gate series resistor 8. The power semiconductor chip 1 is a chip in which a main switch unit 5, a sub-switch unit 6 and a current detection resistor 7 are integrated. The main switch unit 5 and the sub-switch unit 6 are each an IGBT. The power semiconductor chip 1 and the hybrid integrated circuit 2 are sealed by a resin module 9, being connected to each other by bonding wires 10, which also connect the power semiconductor chip 1 and the ceramic board 2 to external terminals. The power semiconductor chip 1 and the ceramic board 2 are joined to a metallic base 11. In the configuration described above, the gate series resistor 8 also referred to as a gate protection resistor is normally created on the hybrid integrated circuit 2 as a thick-film resistor to provide endurance against a surge. Such a gate series resistor 8 is an excellent means for realizing a low-cost monolithic IC chip with a reduced magnitude of a surge to be endured in the control semiconductor chip.
The semiconductor power module modularizing the control semiconductor integrated circuit and the power semiconductor switching-device of these types is commonly known as a multi-chip semiconductor power module. By using the semiconductor power module with such a multi-chip configuration, the control semiconductor chip implementing the control semiconductor integrated circuit can be thermally separated from the power semiconductor switching-device, which dissipates a lot of heat. In addition, the power semiconductor chip, which implements the power semiconductor switching-device, and the control semiconductor chip can be fabricated in manufacturing processes optimum for the chips. Further, as a whole, the power semiconductor chip and the control semiconductor chip can be implemented as a single circuit component.
However, in the conventional semiconductor power module described above, the thick-film resistor in the hybrid integrated circuit serves as the gate series resistor cited above. Thus, the hybrid integrated circuit 2 or the ceramic board 2 becomes large in size, raising a problem that it is difficult to reduce the size of the semiconductor power module and impossible to implement a high-density device.
In addition, in the semiconductor power module including the hybrid integrated circuit, the substrate of the gate series resistor is connected to a gate in the power semiconductor chip by a bonding wire. Thus, the semiconductor power module has a problem that a surge current input through the gate series resistor increases a surge voltage applied to the gate in the power semiconductor chip due to another surge voltage generated by the surge current at the inductor of the bonding wire. That is, an input surge voltage that should naturally be attenuated by an effect provided by a low-pass filter circuit comprising the gate-series resistor and the capacitance of the gate is increased. It is to be noted that the surge voltage is input from a control input terminal of the semiconductor power module.